Adding panels for trove

* Add python-troveclient to requirements.
* Add trove api to openstack_dashboard apis.
* Add Database Instances panel.
* Add Database Backups panel.

Authors:
* Robert Myers
* Denis Makogon
* Andrea Giardini

Implements: Blueprint trove-support

Change-Id: I0541534612ccb491d692168c3c9ca7a841650be6
Merge "Adding panels for trove"